1. Field of the Invention
This invention relates to a method of determining transmission channels in the optimal order to prevent interference problems in a multi-station communications system, and more specifically to a method of allocating transmission channels in the optimal order according to priority assigned to each channel. This invention will be discussed in connection with a mobile radio communications system, however, it should be noted that it is applicable to a LAN (Local Area Network) as well.
2. Description of the Prior Art
It is known in the art to apply frequency reuse in a mobile radio communications system in order to satisfy various objectives such as large subscriber capacity, efficient spectrum use, widespread availability, adaptability to traffic density, etc. The frequency reuse refers to the use of channels on the same radio carrier frequency to cover different area which are separated from one another by sufficient distances so that cochannel interference is not objectionable. A system utilizing such concept is known as a cellular land mobile radio system. For further data relating to the frequency reuse, a reference should be made to an article entitled "Optimal Channel Reuse in Celluar Land Mobile Radio Systems", IEEE Transactions on Vehiclular Technology, Vol. VT-32, No. 3, August 1983, Pages 217-224.
Through frequency reuse, the cellular mobile radio communication system can handle a number of simultaneous calls greatly exceeding the total number of allocated channel frequencies. If the traffic demand in some cell reaches the capacity of that cell, the cell requires a revision of cell boundaries so that the area formerly regarded as a single cell contains several cells.
Subdividing the cell, however, tends to accelerate the difficulty of defining the cell boundaries due to varying transmission characteristics which are caused by tall buildings, other facilities and so on. As a result, in order to reduce cochannel interferences, the same channel set should be allocated to adequately separated cells, which in turn reduces the effects of frequency reuse.